A background calibrated 28GS/s 8b interleaved SAR ADC in 28nm CMOS

A 28-GS/s time-interleaved ADC suitable for PAM4 optical and backplane applications is presented. The architecture uses a two-rank 2×(4:4) sampling network to interleave 32 8b SAR ADCs employing redundancy to relax DAC settling requirements. A DSP core estimates and corrects the gain, offset and timing error between channels. An ENOB of 5.8b and 5.4b is achieved with 1-GHz and 13.3GHz input signals. The ADC consumes 165-mW from a single 950-mV power supply and is fabricated in a 28nm CMOS process occupying 0.24mm
²
.